WO 2005/026553 A1 describes variable displacement vane pumps with a pressure control system for controlling the discharge pressure of the lubricant. The pressure control system comprises a first control chamber wherein a first plunger is provided which is movable axially. The first control chamber is connected via a first pressure conduit with the pump outlet. The pressure control system also comprises a separate control element which is realized as a cylinder-piston-element which keeps the pressure of the pressurized lubricant provided by the pump at a more or less constant level. This is realized by opening and closing a control outlet of the control chamber, thereby allowing the stator ring to move into a low pumping volume direction or being pushed into a high pumping volume direction.
The pressure control is independent from other parameters, such as lubricant temperature or others.